A super-resolution microscope has been recently developed which is based on spectroscopic processes inducing the fluorescence depletion effect by two-color laser light (see, for example, Patent Document 1). In such a super-resolution microscope, it is essential to use a two-color phase plate which does not modulate the phase of a pump beam (first illumination light beam) but can modulate only an erase beam (second illumination light beam). Only one phase plate is required to be inserted into an optical system of a commercially available laser microscope to focus the pump and erase beams onto a sample without misalignment, which makes it possible to achieve spatial super-resolution corresponding to design values without the need for complicated optical adjustment.